Various methods for removing or building up material layers for semiconductor devices are known. Physical vapor deposition (PVD) methods are often used in the semiconductor industry.
Dielectric PVD sputtering has many applications in the semiconductor industry, such as, for example, hafnium oxide, tantalum oxide, aluminum oxide for Resistive random-access memory (ReRAM) and conductive-bridging random-access memory (CBRAM) filaments, magnesium oxide for STT-RAM barrier layers, tantalum oxide and titanium oxide for antireflection layers for image sensors, etc. Dielectric materials may be deposited using reactive sputtering, where a metallic conductive target is used and reacts with an oxygen or nitrogen plasma to deposit dielectric, or using a composite non-conductive target with RF power (either capacitive or inductive coupling) to directly sputter the target materials onto the substrate. The second method is typically used for applications in which substrate oxidation or nitridation during the dielectric deposition is not desirable, barring the use of reactive gases in such applications. Although techniques to produce dielectric films using reactive sputtering exist, the inventors have observed that there are still many challenges facing direct dielectric target sputtering using RF plasma, including deposition rate drifting as the process kit life progresses, worsening defect performance, and worsening uniformity.
To address the above-noted issues, an angled multicathode chamber is used. A dielectric target is connected to an RF power supply, and a metallic target is connected to a DC power supply. A rotating shield is used to avoid cross-contamination between the targets during sputtering. The purpose of the metallic target is to paste the shield to recover the deposition rate due to grounding loss caused by dielectric coating. The metallic paste also helps prevent the peeling and flaking of dielectric particles on the shield.
However, the inventors have observed several drawbacks with the above design. Firstly, a large amount of paste is typically needed to serve the above-noted purpose because the dark space area surrounding the target, especially the side wall of the hole in the shield, needs to be sufficiently covered in order to recover the deposition rate. Secondly, contamination of the metallic target is inevitable due to RF sputtering of the dielectric material deposited on the dark spacing area surrounding the target. Typically, some dielectric material is sputtered onto the shield and shutter to allow the paste material to be covered by a thin layer of dielectric to reduce contamination before sputtering the dielectric on the substrate. However, the inventors have observed that the sputtering of some dielectric material onto the paste material will make the chamber particle performance worse. Finally, another drawback of the above apparatus is that the potential of the grounded shield, acts as a negative potential relative to the plasma's positive potential, resulting in the sputtering of materials that have previously been deposited on parts of the shield. Consequently, the inventors have observed that the substrate becomes contaminated due to the pasted metal on the shield being sputtered onto the substrate.
Therefore, the inventors have provided embodiments of an improved method and apparatus for processing a substrate.